I. Field of the Invention
The present invention relates to data communication. More particularly, the present invention relates to novel and improved techniques to control transmissions in a variable rate communication system.
II. Description of the Related Art
A modern day communication system is required to support a variety of applications. One such communication system is a code division multiple access (CDMA) system that supports voice and data communication between users over a terrestrial link. The use of CDMA techniques in a multiple access communication system is disclosed in U.S. Pat. No. 4,901,307, entitled “SPREAD SPECTRUM MULTIPLE ACCESS COMMUNICATION SYSTEM USING SATELLITE OR TERRESTRIAL REPEATERS,” and U.S. Pat. No. 5,103,459, entitled “SYSTEM AND METHOD FOR GENERATING WAVEFORMS IN A CDMA CELLULAR TELEPHONE SYSTEM.” Another specific CDMA system is disclosed in U.S. patent application Ser. No. 08/963,386, entitled “METHOD AND APPARATUS FOR HIGH RATE PACKET DATA TRANSMISSION,” filed Nov. 3, 1997, now U.S. Pat. No. 6,574,211, issued Jun. 3, 2003 (the HDR system). These patents are assigned to the assignee of the present invention and incorporated herein by reference.
CDMA systems are typically designed to conform to one or more standards. Such standards include the “TIA/EIA/IS-95-B Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System” (the IS-95 standard), the “TIA/EIA/IS-98 Recommended Minimum Standard for Dual-Mode Wideband Spread Spectrum Cellular Mobile Station” (the IS-98 standard), the standard offered by a consortium named “3rd Generation Partnership Project” (3GPP) and embodied in a set of documents including Document Nos. 3G TS 25.211, 3G TS 25.212, 3G TS 25.213, and 3G TS 25.214 (the W-CDMA standard), and the “TR-45.5 Physical Layer Standard for cdma2000 Spread Spectrum Systems” (the cdma2000 standard). The HDR system can be designed to conform to the specifications defined in a document entitled “HDR Air Interface (HAI) Specification” (the HAI specification), which has been provided to the 3GPP2/TSG-C standard body and is the basis for development of a final standard. These adopted and proposed standards are incorporated herein by reference.
Newer generation CDMA systems are typically capable of supporting a number of data rates that typically include a high maximum data rate. For example, the HDR system can be operated to transmit data at rates ranging from 38.4 Kbps up to 2467.6 Kbps. This wide range of data rates is especially effective for data communication, which is typically characterized by long periods of silence punctuated by large bursts of traffic.
In some CDMA systems such as the HDR system, a large portion of the available system resources can be used to transmit to a single remote terminal for a particular time period to support a high peak data rate. However, possibly for costs and other considerations, many remote terminals may be designed to support a particular average data rate, which is typically only a fraction of the peak data rate. For these remote terminals, sustained transmission at a data rate higher than the supported average data rate may result in the transmitted packets being dropped or received in error. When this occurs, valuable system resources are wasted by transmitting to remote terminals not capable of processing the transmission.
As can be seen, techniques to control transmissions in a variable data rate communication system based on the capability of the remote terminals and such that the available system resources are efficiently utilized are highly desirable.